Applied Mechanics and Materials Vols. 347-350

Abstract: Turbo codes have a wide range of applications in 3G mobile communications, deep-sea communications, satellite communications and other power constrained fields. In the paper, the Turbo Code Decoding Principle and several major decoding methods are introduced. Simulations of Turbo code performance under different parameters of AWGN channel are made and the effects of the different interleaving length, the number of iterations, and the decoding algorithm to Turbo code performance are also discussed in AWGN channel. Simulation results show that under the same signal-to-noise ratio, the more the number of iterations is, the longer the sequence of information is, and the more excellent decoding algorithm is, the better the performance of Turbo codes is.

Abstract: Wireless communication and multimedia applications feature a large amount of matrix operations with different matrix size. These operations require accessing matrix in column order. This paper implements a Multi-Grained Matrix Register File (MMRF) that supports multi-grained parallel row-wise and column-wise access. We implement a 4*4 MIMO decoding with the help of MMRF to illustrate the efficient matrix operations on SIMD processors. Experimental results show that, compared with TMS320C64x+, our SIMD processor can achieve about 5.65x to 7.71x performance improvement by employing the MMRF. By customized design technology, we reduce the area and critical-path delay of MMRF by 17.9% and 39.1% respectively.

Abstract: Energy scarcity is one of the most critical problems that occur in wireless sensor networks compared to traditional networks. However, the problem has been partly solved by building the power consumption model of WSN. This paper is based on a simple wireless sensor network model, it gives the optimal location of the CH nodes in a cluster and the best parameter about how to divided the cluster amongst hierarchy networks. As shown last, the proposed scheme can save up to 95% of power consumption.

Abstract: Wireless sensor networks comprise of minor battery driven devices with restricted energy resources.Once installed,the minor sensor nodes are usually unapproachable to the operator, and thus auxiliary of the energy source is not practicable.Hence,energy proficiency is a vital design issue that needs to be boosted in order to increase the lifetime of the network. LEACH is a popular hierarchical routing protocol which efficiently maintains the energy storage of nodes in Wireless Sensor Network (WSN).The nodes using LEACH are divided into clusters.The advantage of LEACH is that each node has the equal probability to be a cluster head,which makes the energy dissipation of each node be relatively balanced. This paper studies LEACH protocol, and focuses on how to decide the next hop nodes more reasonable when the data are transmitted at the steady state. Simulation has been done in NS2 and the results show that the algorithm after improved is more energy-efficient than LEACH protocol.

Abstract: For the superheterodyne reconnaissance receiver detected "signalBatch-increasing" phenomenon, research on radar signal sand the intercepted characteristics of reconnaissance receiver from the frequency domain, pointed out that "Pulse-width split" and "Pulse-width truncated" caused by Emitter signal spectrum loss is the reason of "Batch-increasing",On this basis, analyzed the strategies of "Batch-increasing" signal processing .

Abstract: The combinations of MIMO (Multiple-Input-Multiple-Output) and UWB (Ultra-Wide-Band) systems greatly improve the performance of the UWB system. For the MIMO-UWB system, a new decoding scheme is proposed based on the STF (Space-Time-Frequency) coding and it can reduce the decoding complexity. The simulation results show that under the same SNR, the new method can obtain better performance of the bit error rate than the traditional ML decoding method.

Abstract: Based on current situation of mobile equipments earth devices, a new type of portable horizontal grid earth electrode has been designed. With the impulse ground measurement system, different number of earth electrodes responses to double exponential pulse current have been tested on cement grounds. Impulse waves of voltage and current have been gotten by experiments, and the curve of Transient Grounding Resistance (TGR) can be calculated. The analysis of discharging capacity of horizontal grid earth electrodes in time domain has great significance in the design of mobile equipments earth devices.

Abstract: The microstrip circuit is mostly analyzed in transform domain, because its equivalent circuit equation is often nonlinear differential equation, which is easily analyzed in transform domain relatively, but hardly did in time domain, so the analysis of microstrip circuit is a hard work in time domain. In this paper, the FDTD method is used to analyze the microstrip circuit in time domain, by transforming the nonlinear differential equation into time domain iterative equation, selecting suitable time step, and having an iterative computing, the time domain numerical solution can be solved. The FDTD method analyzing the microstrip circuit provides a new way of thought for analyzing microstrip circuit in time domain.

Abstract: Frequency locked loop (FLL) plays an important role in carrier synchronization because of its excellent dynamic performance. However, it performs inadequately in low signal-to-noise ratio (SNR). In this paper, the principle of stochastic resonance (SR) is briefly introduced and a SR processor is proposed. Based on traditional FLL, the SR processor is added before frequency discriminator in order to weaken the effect that thermal noise brings to FLL. The paper investigates the processing effect of SR. Simulation results show that the performance of improved FLL is greatly improved. It can tolerate rather high dynamics and tracking accuracy of frequency achieve 0.2Hz even with CNR as low as 25 dBHz, which verified the validity of above ideas.

Abstract: An unsymmetrical Doherty power amplifier (DPA) at 460MHz is presented in this paper. The carrier and peaking amplifier of the DPA, which base on two equal-sized devices, are matched with different networks to mitigate the performance degradation caused by the limited load modulation. Measured with continuous wave (CW), the unsymmetrical DPA saturates at an output power of 49.2dBm and achieves a drain efficiency of 51% at 6dB back-off. Using a one-carrier long term evolution advanced (LTE-Advanced) signal with 20MHz bandwidth, the unsymmetrical DPA exhibits a drain efficiency of 48.7% at an average output power of 42.1dBm, along with adjacent channel leakage ratio (ACLR) of-34.1dBc and-53.3dBc before and after digital pre-distortion (DPD), respectively.